1. Field of the Invention
This invention relates generally to chair seat adjustment mechanisms and in particular to a mechanism that allows the horizontal fore and aft position of the chair seat to be adjusted relative to the base of the chair.
2. Description of Related Art Including Information Disclosed Under 37 C.F.R. xc2xa7xc2xa71.97 and 1.98
There are many devices for adjusting a chair seat in the horizontal direction. Such devices are found in U.S. Pat. Nos. 6,027,168; 6,099,076; 5,755,490; and 5,035,466.
Each of these devices requires a mechanical movement of a locking lever of some type to hold the seat in place in a selected horizontal position. Many of these mechanical devices are very complicated and thus expensive to manufacture and are sometimes very bulky and difficult to use.
It would be advantageous to have a chair seat horizontal adjustment mechanism that in one embodiment does not require any mechanical operation of a lever or such device by the user and in another embodiment has a very simple lever mechanism to enable movement of the chair seat.
The present invention has a rigid seat plate that forms a base for a chair seat. A seat pan, having a front portion and a rear portion, is mounted on top of the seat plate. A stop strip or brake pad having a high coefficient of friction is placed between and attached to one of the seat plate and the seat pan. At least one slot extends longitudinally in the seat plate at least partially between the front and rear seat pan portions. A screw and spring assembly in the form of a resilient means extends through the at least one slot for holding the seat pan to the seat plate with the brake pad therebetween to prevent relative movement between the seat pan and the seat plate. The resilient means or spring enables the forward portion of the seat pan to be lifted so as to separate the brake pad from the other one of the seat plate and seat pan to allow the seat pan to move forwardly and rearwardly along the at least one slot with respect to the seat base to adjust the seat horizontal position. In the preferred embodiment, at least two parallel-spaced, longitudinally-extending slots are formed in the seat plate and first and second screw and spring assemblies extend through each of the parallel-spaced slots and the seat plate, respectively, for threadedly engaging the seat pan while enabling the front portion of the seat pan to be urged against the spring assembly and to separate the brake pad from the other one of the seat pan and seat plate to allow the seat pan to move forwardly and rearwardly about the resilient means to adjust the seat position. In addition, third and fourth screw assemblies may be mounted in the at least first and second parallel-spaced slots in the rear portion of the seat pan for resiliently holding the rear portion of the seat pan to the seat plate so as to enable the front part of the seat pan to be moved vertically to separate one of the seat pan and the seat plate from the brake pad.
The third and fourth screw assemblies comprise a screw having a head portion and a threaded portion for extending through the at least first and second spaced parallel slots in the seat plate to threadedly engage the seat pan. A washer, having a low coefficient of friction, is placed on the screw and engages the seat plate. A resilient spacer surrounds the screw between the washer and the screw head portion such that when the forward portion of the seat pan is lifted substantially vertically, the resilient spacer is at least partially compressed on at least one side thereof thereby allowing the seat pan to pivot in the vertical direction substantially about the third and fourth screw assemblies to separate the brake pad from the other one of the seat plate and the seat pan.
The brake pad is in the form of an elongated rectangular friction strip that extends laterally across one of the seat pan and the seat plate and is rigidly attached thereto. The elongated brake pad friction strip is attached to one of the seat pan and seat plate forwardly of the first and second screw and spring assemblies. In the preferred embodiment, the elongated friction brake pad strip is xe2x85x9c inch wide and 8 inches long, although both of the length and the width could vary. Further, in the preferred embodiment, the elongated friction pad strip is rigidly attached to the seat plate, although it can be rigidly attached to the seat pan. Further, in the preferred embodiment, the seat plate is formed of aluminum, but it could also be formed of high-impact plastic.
In a second embodiment, a simple arrangement is provided wherein the friction lock between a seat plate support and a seat pan support can be mechanically released such as by a lever, push-rod, cable, or the like.
Thus, it is an object of the present invention to provide a locking device for horizontal seat positioning on a chair that utilizes a friction pad between the seat plate and the seat pan and an attaching means that will allow the front portion of the seat pan to be lifted, thus separating the seat pan from the friction pad and allowing the seat pan to be adjusted relative to the seat plate. It is another object of the present invention to provide a friction held seat plate support and a seat pan support that can be released by a slight arcuate movement of a mechanical device to enable horizontal sliding of the chair seat for adjustment purposes.
It is also an object of the present invention to place the friction pad forward of the first and second screw and spring assemblies.
It is also an object of the present invention to attach the elongated friction pad strip rigidly to the seat plate.
Thus, the present invention relates to a locking device for horizontal seat positioning on a chair having a forward and a rear portion comprising a rigid seat plate forming a base for a chair seat, a seat pan having a front portion and a rear portion, mounted on top of the seat plate; a brake pad having a high coefficient of friction placed between, and attached to one of, the seat plate and the seat pan; at least one slot extending longitudinally in the seat plate at least partially between the front and rear seat pan portions; and resilient means extending through the at least one slot for holding the seat pan to the seat plate with the brake pad therebetween to prevent relative movement between the seat pan and the seat plate, but also enabling the forward portion of the seat pan to be lifted so as to separate the brake pad from the other of the seat plate and seat pan to allow the seat pan to move forwardly and rearwardly in the at least one slot with respect to the seat base to adjust the horizontal seat position.
The present invention also relates to a locking device for horizontal seat positioning on a chair having a seat plate support and a seat pan support that are held together in a friction arrangement by a screw non-rotatably attached to the bottom of the seat pan support, the screw having external threads facing downwardly toward the seat plate support, a selectively rotatable brake attached to said seat pan support and having internal threads for threadable attachment to the external threads of the non-rotating screw, an activating mechanism is attached to the brake such that with minimal rotation of said brake, the frictional coupling between the seat pan support and the seat plate support is released thereby allowing movement of the seat pan support with respect to the seat plate support.